In general, a method for measuring properties of an analyte by holding the analyte on a void-arranged structure, applying an electromagnetic wave to the void-arranged structure holding the analyte and analyzing a transmittance spectrum thereof is employed in order to analyze properties of a substance. More specifically, a technique of analyzing a transmittance spectrum by applying a terahertz wave to a metal mesh filter to which protein or the like employed as an analyte adheres can be cited, for example.
As the prior art of such a technique of analyzing a transmittance spectrum with an electromagnetic wave, Japanese Patent Laying-Open No. 2008-185552 (Patent Literature 1) discloses a method constituted of a void-arranged structure (more specifically, a meshy conductor plate) having a void region, an analyte held on the surface of the void-arranged structure, an electromagnetic wave application portion applying an electromagnetic wave toward the analyte and an electromagnetic wave detection portion measuring the electromagnetic wave transmitted through the void-arranged structure for measuring properties of the analyte on the basis of that the electromagnetic wave projected from the electromagnetic application portion toward the void-arranged structure is inclined incident upon a plane including the void region and the position of a dip waveform caused in a frequency characteristic of a measured value moves due to the presence of the analyte (FIGS. 3 and 9 of Japanese Patent Laying-Open No. 2008-185552).
In a measurement method for determining the analyte from a quantity of change (quantity of shifting of a reverse peak) in a frequency corresponding to the minimum of the dip waveform in a transmittance spectrum obtained from the aforementioned transmittance at a time of changing the frequency of the aforementioned electromagnetic wave as applied in a constant range, however, it has been difficult to determine an analyte of a small quantity (particularly not more than about 100 ng/mm2) since the quantity of shifting of the reverse peak reduces and becomes smaller than the detection limit (frequency resolution) (refer to FIG. 9 of Japanese Patent Laying-Open No. 2008-185552). Further, such a method requires a mechanism for acquiring information of the frequency, and hence a measuring apparatus such as a spectrometer, for example, large-sized and hard to control is required.
PTL 1: Japanese Patent Laying-Open No. 2008-185552